Field of the Invention
This disclosure relates to the field of cardiovascular exercise machines. In particular, to elliptical style machines or gliders that have an adjustable stride length.
Description of the Related Art
The benefits of regular aerobic exercise on individuals of any age is well documented in fitness science. Aerobic exercise can dramatically improve cardiac stamina and function, as well as leading to weight loss, increased metabolism and other benefits. At the same time, aerobic exercise has often been linked to damaging effects, particularly to joints, bones, or similar structures where the impact caused by many aerobic exercise activities causes damage. Therefore, those involved in the exercise industry are continuously seeking ways to provide users with exercises that have all the benefits of aerobic exercise, without the damaging side effects.
Most “low-impact” aerobic exercise has traditionally been difficult to perform. Many low-impact aerobic exercises (such as those performed in water) traditionally require performance either outside or at a gym where special facilities which partially support a user's body mass can be provided. Cold weather, other undesirable conditions, and cost can make aerobic exercise unobtainable at some times and to some people. In order to allow people to perform aerobic exercises without having to go outside or to gyms or the like, fitness machines have been developed to allow a user to perform aerobic exercises in a small area of their home.
Many of these machines, however, traditionally suffered from either being relatively high-impact, or from being complicated to use and understand. While devices like treadmills can provide lower impact walking or running compared to exercising on city streets because they can have shock absorbing structures built into them, they are often still not low impact. Further, lower impact machines, such as those designed to simulate cross country skiing, can be difficult to use as they require the user to engage in a somewhat unnatural and complicated motion. In either of these cases, the fitness machine often becomes a coat rack instead of being used for its intended purpose.
Recently, there has been introduced a class of machines that have produced lower impact workouts while still maintaining a more natural motion. These are often referred to as “elliptical machines”, “elliptical cross-trainers”, or “gliders” and have become very popular due to their ease of use and their provision of relatively low-impact aerobic exercise. Generally in these types of machines, a user performs a motion using their legs that forces their feet to move in a generally elliptical, racetrack, oval, or elongated circular motion about each other. This motion is designed to simulate the motion of the feet when jogging, walking, or climbing but the rotational motion is “low-impact” compared to jogging or climbing where the feet regularly impact a surface.
In an elliptical machine, the user's feet do not leave the footpads of the machine in most cases and the footpads smoothly travel through a defined path reducing or eliminating impacts from the user's feet striking the surface. In many respects, the motion could be considered more akin to a pedaling motion than a walking motion, but because the exercise is performed standing up, and with an elongated elliptical motion as opposed to a circular pedaling motion, the motion feels more like a striding walk or “glide”.
While elliptical machines have become common in most gyms and with home users, one problem with traditional elliptical machines is that the dimensions of the path traversed by the user's feet are generally severely limited in size and shape by the design of the machine. The ellipses generated by these machines are often created by the interaction of a plurality of different partial motions, and attempts to alter the motion of a user in one dimension often alters the motion in another as well. For example, in many machines, altering the length of stride requires altering the diameter of a wheel or crankshaft, which in turn alters the height of the motion a similar amount. This “fixed ratio” movement is problematic because users come in a variety of shapes and sizes. Smaller female users often have a shorter stride length than a lot of the male users. Users, therefore, desire the option to arrange the machine so that the ellipse can be tailored to fit their stride. This allows a machine to be a better fit for all the users in a gym or household. However, with machines on the market today, such customization is generally not possible.
The problem is most simply understood by looking at the motion the feet make when using an elliptical exercise machine. This motion can be generally described by the dimensions of the ellipse. Since users generally stand upright on elliptical machines, the user's feet travel generally horizontally relative to the surface upon which the machine rests. This represents the users stride length or how far they step. Further, the user's feet are raised and lowered relative to the surface as they move through the ellipse. This is the vertical change through which the user's feet pass. In an elliptical machine, it will generally be preferable that the length of the user's stride be greater than the height the user's feet are lifted when the user is “striding” on the machine as this best corresponds to the actual motion of the feet when walking or performing an activity, such as cross country skiing. Alternatively, shortening the stride is more akin to stair climbing where the vertical and horizontal movement is generally similar.
While stride length is often personal and is based on the length of the user's legs and their personal flexibility, it should be recognized that within the available strides for any user, different types of strides, be it gliding or stepping, can be desirable to provide for the workout of different muscle groups as well as different levels of strenuousness, both between and within exercise sessions. For this reason, it is often desirable to provide for an elliptical trainer that can provide for a variety of different stride lengths.
A number of different types of machines have been proposed which provide for variable stride length. However, these have generally not provided for mechanical robustness or desirable adjustment to a user. In a first instance, the user of an elliptical that desires adjustable stride length will generally want to have the length be adjustable quickly and across a wide range of motion. Slow adjustment means that it is difficult, and can be uncomfortable, to tailor intervals in a workout. Many workout plans utilize rapid changes between different types of exercises (e.g. traditional interval workouts where high speed flat surface motion is interspersed with lower speed inclined motion) and often change between intervals quickly with a user only participating in any interval for a couple of minutes.
Traditional adjustable stride machines often need time to provide adjustment and simply cannot cater to the quick changes desired in many training programs. Stride adjustments traditionally rely upon adjusting an internal angle, or similar component, of a composite motion to provide that the orientation of a related part also changes. The problem with a quick adjustment is that the motion needs to be smooth and performable while the machine is in motion (being exercised upon) while at the same time be sufficiently mechanically robust that the adjustment is comfortable to the user and does not risk damage to the machine when having to re-orient machine components and the mass of the user. Traditionally, to make the motion smooth and safe, devices have had relatively slow transitions. While there is some mechanical advantage where a relatively small motion of a drive mechanism can create a relatively large motion change to a user, the motion to the user is still generally slow.